The present invention relates to a microwave plasma processing method and, more particularly, to a microwave plasma processing method using an ECR discharge.
A prior microwave plasma processing method, such as the method disclosed in Japanese Patent Laid-open (Kokai) No. 60-154620, creates a magnetic field within a gasfilled discharge tube using a solenoid, introduces a microwave into the discharge tube to produce a plasma within the discharge tube by the interaction between the magnetic field and the microwave, and processes a workpiece with the plasma. When processing a workpiece with a plasma, this prior microwave processing method varies the amplitude of the current flowing through the solenoid to vary the magnetic flux density of the magnetic field in order that a maximum plasma density region in the plasma density distribution oscillates between a central region and a peripheral region of the object surface the workpiece to apply a plasma having a substantially uniform plasma density distribution to the object surface of the workpiece, thereby improving the uniformity of processing.
However, this publication No. 60-154620 teaches nothing about the etch selectivity between the mask of the workpiece and an underlying layer, the production of etch residue, a laminated film for the enhancement of the reliability of metal wiring lines and the like. In this prior method, the density distribution of a plasma moves to the central portion or the peripheral portion of the object surface according to the gradient of the magnetic field and the method is not devised for the optimization of the plasma when the workpiece is changed. Therefore, it is difficult to determine process conditions capable of improving the etch selectivity between the mask and the underlying layer and enabling processing without producing an etch residue, when the prior method is applied to processing a workpiece having a minute configuration or to processing a laminated workpiece.